Re: Linked Lists

Charlie Johnson wrote:


The class doesn't reference itself. An object holds a reference to an object.

There is no reason an object can't hold a reference to itself; in fact, every
object does, known by the keyword 'this'.

Explicit references, like 'next' in your example, are almost always going to
point either to 'null', or to another instance of the class. That is another
separate instance of the same class.

So when you create a LinkedList *instance*, it holds a reference 'next' to
another LinkedList *instance*. Or to 'null'.

Let's flesh out the example.

<sscce name="LinkedNode.java" >
package testit;
public class LinkedNode <T>
{
   private final T info;
   private LinkedNode <T> next; // members start out null in Java

   public LinkedNode( T value )
   {
     info = value;
   }

   public void setNext( LinkedNode <T> node )
   {
     this.next = node;
   }

   public LinkedNode <T> getNext()
   {
     return next;
   }

   public T getInfo()
   {
       return info;
   }

   public static void main( String [] args)
   {
     LinkedNode <Integer> head = new LinkedNode <Integer> ( 23 );

     LinkedNode <Integer> another = new LinkedNode <Integer> ( 17 );
     another.setNext( head );
     head = another;

     another = new LinkedNode <Integer>( 497 );
     another.setNext( head );
     head = another;

     for( LinkedNode <Integer> walker = head;
          walker != null;
          walker = walker.getNext() )
     {
       System.out.print( " => " );
       System.out.print( String.valueOf( walker.getInfo() ) );
     }
     System.out.println();
   }

}
</sscce>

--
Lew